Photographic emulsion containing thiazolocarbocyaning dyes



Patented Sept. 11, 1.934`

'PHOTOGRAPHIC EMULSIO CONTAINING THIAZOLOCARBOCYANINE DYES Leslie (t. s. Brooker, Rochester, N. Y., assigner to Eastman Kodak Company, Rochester, N. Y., a corporation of New York e Application June 29, 1932, Serial No. 619,963

13 Claims. (Cl. 95-7) This invention relates to photographic emul- It is, therefore, among the objects of the pressions and more particularly to gelatino-silverent invention to prepare photographic emulsions halide emulsions sensitized with a new class of sensitized with a, new class of dyes, namely, 7- dyesy namely, 7 substituted thiazolocarbOCysubstituted thiazolocarbocyanines, and photoamines. i graphic elements coated with such emulsions.

In my co-pendmg apphcation No. 548.026, it otherobjects wi11 appear upon a further perusal was mentioned that certain dyes, for which the of this Specification llam "neOthiaZOlOCal'bOCyanne is Proposed, The thiazole bases with a reactive methyl could be prepared from bases of the thiazole segroup in the 2 p0siti0n may be givenvthe gem i0 ries. It was further stated in that application eral formulathat these neothiazolocarbocyanines were prow duced when certain alkyl quaternary salts of the A\ /S thiazoles weretreated with ethyl orthofornate C51\C in pyridine solution. The alkyl quaternary salts 4 2 CH i.; of the bases which are most suitable for the B/ preparation of the neothiazolocarbocyanines are thoseof alkyl sulfuric acids, or better still, aryl- Where A and B represent univalent atoms or sulfom'c acids. It was further mentioned in my groups such as hydrogen aliphatic or aromatic. above application that in general, a proportion grouping The numbering is that in Common o of normal thiazolocarbocyanine accompanied usage for bases of this type, being that used,

the neothazoloca'rbocyane and in n lost in' for instance in Richters Lexikon der Kohlenstoff stances the normal thiazolocarbocyamne was Verbindungen.

more soluble than the neothiazolocarbocyanine The base 2 meth ylthiazole, or a substituted 2- and the latter could therefore be read1ly obtained methyithiazoie, e g. 2 methyi 4 phenyithiazoie mit sait; gifzaelltixn additionthat the norma-i1 may be converted into an alkylquatemary sa 75 by heating it with, for instance, a dialkyl sulfate lgogrxgiriziliidwliagasw; l or an alkyl p-toluene sulfonate or an alkyl iodide. densed in the presence of alkyl orthoformate and Whenth? alkyl hahdes arehfld qatmar 30 pyridine. As .herein described, alkyl ortho-esters alkyl lodldes are produced W 1C. 0n eea men 80 of a mono-carboxylic acid having more than one Wlth ethylorthffflmae and Dylldlne lmderapcarbon atom yield 7substituted thiazolocarbo- DTODIate C011d1t10nS-Y1e1d thlaZOlOCaIbOCYamneS. i cyanines. These are related to the neothiazolo- The general reactwn `0f alkyl Quaternary Salts carbocyanines in that both dyes have a univalent of 2-methy1thia20'1es Wlth alkyl 01121.10 esters of 35 group attached to the carbon atom in the 7- the monocarboxyllc acids may be written as fol position. lows- 'various methods of double decomposition.

preparation of orthoesters of monocarboxylicacids (see my U. S. Patents Nos. 1,846,301, 2, 3 and 4) which may be used so as to give ortho esters -in which R1 and R2 are similar or dissimilar but,`

as may be`seen from theequation, these alkyl groups are removed as molecules of alcohol and do not enter the dye molecule. D is a suitable y univalent atom or group, such vas hydrogen, alkyl or aryl. If D be hydrogen then the ester employed is derived from orthoformic acid and X is J best chosen as iodide for the main product of the reaction to be normal thazolocarbocyanine of `the type:

. A\({s\ n /B/A- -oH=oH-CH= y) B/ \N/ f .\N/ \B l R R as has already been explained, since choice of, for example p-toluenesulfonate for X results in a preponderance of the special type of rI-substituted thiazolocarbocyanines known as neothiazolocarbocyanines. In most cases however, some normal thiazolocarbocyanine is produced even when X is p-toluenesulfonate or alkylosulfate, but if the normal compound is desired, it is recommended that iodide be chosen for X and this results in the product insgeneral being almost pure normal compound.

If D represents a univalent group such as methyl orethyl (CI-Iaor C2H5) then it is immaterial whether X represents halide, p-toluenesulfonate, alkylosulfate or the like, as far as the type of compound is concerned. In all cases the 7-sub stituted dye is produced. The yield of product,

however, may vary with the acidic radical em' ployed, and in general an aryl sulfonic radical is preferred for the condensations.

The 2-methylselenazoles may be regarded as thiazoles in which the sulfur atom in the molecule has been replaced by a selenium atom. These new bases are described in my co-pending application with-Frank L. White` No. 619,959 illed of even date. Photographic emulsions sensitized with selenazolocarbocyanine dyes derived from the 2-methyl-selenazoles may be prepared in a manner similar to that herein described for the thiazolocarbocyanines. l

In general it is desirable to employ an excess of the ortho ester over the amount (one molecular proportion of ester to two molecular proportions of quaternary salt) shown in the equation. This results in an increase in yield. `f The ortho ester and the quaternary salts are conveniently condensed together by reuxing them together in anhydrous pyridine, usually for an hour or longer. After the reaction is rlnished the dye may be precipitated as atar by the addition of ether, the ethereal layer decanted and the tar dissolved in a little hot alcohol (methyl or ethyl) and precipitated as, for instance, the iodide by an excess of aqueous potassium iodide, or in some cases,

the dye may be precipitated from the pyridine` reaction mixture by the addition vof water, and in still other cases the dye separates from the reaction mixture in the crystalline state. 'I'hese methods are all simple procedures and are' well known -in the art.

' l EXAMPLE I 3,3', 4,4tetramethylthiozolocarbocyanine iodide 2.6 parts of -2,4dimethylthiazole methiodide were reuxed for 5 hours in 30 parts of pyridine with 3 parts of ethyl orthoformate. After allowing the reaction mixture to cool the dye was filtered off and impurities removed by washing with water. The dye was recrystallized from methyl alcohol and was obtained in darkblue needles which gave a crimson solution in the solvent.

EXAMPLE II 2,4-dimethylthiazole ethiodide was made by reuxing the base with ethyl iodide for several days and washing the solid product with acetone to remove starting materials. c

2.7 parts of this' ethiodide were reuxed for 5 hours ywith 30 parts of pyridine and 3 parts of ethyl orthoformate.y The dye was precipitated b'y diluting the reaction mixture with an equal volume of water and allowing to cool. The product was recrystallized from methyl alcohol in which it gave'a crimson solution and was obtained in dark nedles with a greenish reflex.

It has been described in my co-pending appli- 'cation No. 548,026, iiled June 30, 1931, Example IV, that this dye may -also be obtained together with the corresponding neothiazolocarbocyanlne. The almost pure normal thiazolocarbocyanine described in that example may be given a further crystallization to render it completely pure.

EXAMPLE III 4 phenyl 2 methyuhiazole methiodide was v prepared by reuxing equal weights of 4-phenyl 2-methylthiazole .and of methyl iodide for two days. The solid alkyl quaternary salt was re- -gave a crimson solution in methyl alcohol; No

bluish neothiazolocarbocyanine was encountered at all in this preparation.l

EXAMPLE IV f 4,4' diphenyl 3,3'-dethylthiazolocarbocyanine iodide `parts of the salt were heated under reflux with 30 parts of anhydrous pyridine and 3 parts of ethyl orthoformate for 11/2 hours. The reaction 1,973,462 mixture was then diluted with an equal volume of water and allowed -t-o cool. Bronze crystals of the dye separated out which were purified by re- EXAMPLE V 2.25 parts of 2,4-dimethylthiazole were converted into the etho-p-toluenesulfonate of the base by heating it with 4 parts of ethyl-p-toluenesulfonate at 13D-140 C. for six hours. The crude quaternary salt (a viscous melt) was then reuxed without further purification with 20 parts of pyridine and 7 parts of ethyl ortho-propionate for 21/2 hours. After allowing the reaction mixture to cool, the dye was precipitated by the. addition of ether, the ethereal layer decanted ol and the tar dissolved in a little warm methyl alcohol andprecipitated as the iodide by adding thereto a solution of 10 parts potassium iodide dissolved in 100 parts of Water. After allowing the whole to stand aside for several days the dye was removed by filtration and purified by washing followed by recrystallization from methyl alcohol in which it gave a beautiful crimson solution. The dye, after ltration and, airdrying, was obtained as dark needles with a green reflex.

EXAMPLE VI 3.5 parts of 4-phenyl-2-methyl thiazole were converted into the metho-p-toluenesulfonate of the base by heating with 3.7 parts of methyl-ptoluenesulfonate at 100 C. overnight. The crude 4-phenyl-2-methylthiazole metho-p-toluenesulfonate was then reuxed for 90 minutes with 10 parts of pyridine and 4.8 parts of methyl orthoacetate. The dye was then precipitated as the sparingly soluble iodide by double decomposition with a solution of 5 parts of potassium iodide in parts of hot water. The dye separated as a tarry residue, and after the aqueous liquor had been removedthis residue was washed. The purplish black powder was purified by recrystallization from methyl alcohol and the dye was thus obtained as small greenish crystals with a bright lustre. The solution of the dye in methyl alcohol was a crimson color.

EXAMPLE VII 4,4 @phenyl-3,3'-dimethyl-7-ethylth1lazolocarbocyanine iodide 3.5 parts of 4-phenyl-2-methylthiazole were condensed with 3.7 parts of methyl-p-toluenesulfonate as described in Example VI. The quaternary s alt was refluxed without further purification with 5.4 parts of methyl ortho-propionate and 10 parts of pyridine for 90 minutes. The dye was precipitated as the iodide exactly as described for the dye in Example VI and was purified and recrystallized in the saine manner also.' The dye gave a crimson solution in methyl alcohol and crystallized in small green crystals with a green luster.

From the foregoing it becomes apparent that thiazolocarbocyanines may be prepared by condensing two molecular proportions of a 2-methylthiazole alkyl quaternary salt with one molecular proportion of an ortho ester of a monocarboxylic acid. The thiazole may have either hydrogen or a suitable univalent group in one or both of the 4, 5 positions. If an ortho ester of formic acid is employed, an unsubstituted thiazolocarbocyanine will be obtained. If an ortho ester of a monocarboxylic acid other than formic acid is employed, a 7-substituted thiazolocarbocyanine is obtained. These ortho esters are described in my Patents Numbers, 1,846,301, 2, 3 and 4 and need not be repeated here.

The diagrammatic spectrograms constituting the accompanying drawing illustrate the regions of the spectrum to which the various types of dyes herein disclosed will sensitize a gelatinosilver-halide emulsion and the extent of the sensitization at various Wave lengths. The figures y of this drawing and the dye, the sensitizing properties of which each of the Figs. 1 to 6 illustrates, are listed, respectively at the top of each spectrogram. These figures were all taken from silver bromide emulsions which had been bathed in a solution of the dye as herein described; corresponding ones taken from chloride` emulsions vary somewhat but are comparable in region and density.

In the preparation of emulsions containing these photographic sensitizers, it has been found that the dye may be dissolved in methyl alcohol and a volume of solution diluted with water and containing from 5 to 100 milligrams of dye added to 1000 cc. of, for instance, a flowable photo- 4graphic gelatino-silver-halide emulsion, which may then be coated upon a suitable glass or cellulose derivatative transparent support and allowed to dry, the details of which are well known to emulsion experts. While it may not be necessary to add some of the sensitizers in a large amount,

it may be necessary to add others in amounts larger than those given above;` generally about 10 to 20 milligrams is sumcient to obtain the maximum sensitizing effect with a dye having good sensitizing power. The more powerful dyes, however, may require much less. The regulation 0r adoption of the most economical proportions will be apparent to those skilled in the art upon observing the sensitizing power of the particular dye for the particular emulsion in question. The above examples are, therefore, illustrative and not to be understood as limiting the invention in any sense, as it will be apparent that these dyes may be incorporated by other methods in many 0f the photographic. emulsions customarily employed in the art, such for instance as by bathing the plate or film, upon which the emulsion has been coated, in a solution of the dye in an appropriate solvent although this method of incorporating the dye in the emulsion is not to be preferred over that above described. Obviously Vthe claims are all intended to cover any combination of these dyes with a photographic emulsion whereby the dye exerts a sensitizing effect upon the emulsion.

A photographic emulsion in which is incorporated as above described, one or more of the new dyes disclosed herein possesses in general strong sensitivity to the green and orange portion of the spectrum.

Other variations and equivalents will doubtless occur to those skilled in this art, it being understood that the foregoing is stated only to illustrate to those skilled in the art how thiazole alkyl quaternary salts may be condensed withan ortho ester of a monocarboxylic acid to form a thiazolooarbocyanine, and how these new dyes may be utilized to sensitize photographic. emulsions.

What I claim as my invention and desire to se'- cure by Letters Patent of the United States is- 1. A gelatino-silver-halide emulsion which contains a carbocyanine dye of the following struc in which A 4and B represent hydrogen, or aliphatic or aromatic groupings, R equals alkyl, X

equals an acid radlcal and D equals an alkyl group or an aryl group of the benzene series.

2. A gelatino-silver-halide emulsion which contains a carbocyanine dye of the following struc-v ture in which A and B represent hydrogen, or aliphatic or aromatic groupings, R equals alkyl, X equals an acid radical andA D equals an alkyl group.

' 3. A gelatino-silver-halde emulsion which containsa carbocyanine dye of the following structure.

in which A and B represent hydrogen, or aliphatic or aromatic groupings, R equals alkyl, X equals an acid radical and D equals a methyl group.

4. A gelatine-silver-halide emulsion which ccntains a carbocyanine dye ofl the following structure 9. A gelatino-sllver-halide emulsion which contains a- 4,4'diaryl3,3'-dialkyl-'I-alkyl-thlazolocarbocyanine salt.

10. A' gelatina-silver-halide emulsion which contains 4,4'-dimethyl-3,3','l-triethylthiazolocarbocyanine iodide.

11. A gelatiho-silver-halde emulsion which contains 4,4,diphenyl3,3'-7-trimethylthiazolocarbocyanine iodide.

12. A gelatino-silver-halide emulsion which contains 4,4 'diphenyl'3,3 dimethyl- 7 ethylthiazolocarbocyanine iodide.

13. A photographic emulsion comprising a supporting surface coated with a gelatina-silverhalide emulsion which contains a carbocyanine dye of the following structure in which A and B represent hydrogen, or aliphatic or aromatic groupings, R equals alkyl, X equals an acid radical and D equals an alkyl group or an aryl group of the benzene series.

- LESLIE G. s. BROOKER.Y 

